Pump



Patented Dec. 3,1940 i i i UNITED STATES PUlYlP Torbjrn Viktor Dillstrm, Stockholm, Sweden,

assignor to Handelsaktiebolaget Vidar, Stockholm, Sweden, a. corporation of Sweden Application August 10, 1938, Serial No. 224,212

' In Sweden September 28, 1937 9 Claims.

` ber during one delivery stroke of the plunger to a plurality of places of consumption such for eX- ample as the injection nozzles of an internal com- .bustion engine to which liquid fuel is delivered at different times by the pump.

In pumps of the above type a different volume of liquid in the pump chamber is subjected to pressure during each individual delivery period of the pump plunger during the delivery stroke of the plunger, since the liquid delivered during each successive delivery period has to be taken4 from a single charge of liquid in the pump at the commencement of the delivery stroke, which charge is successively diminished by the deliveries effected during the successive delivery periods.

The general object of the present invention contemplates the provision of improved structure for supplying liquid to a plurality of points of consumption, yparticularly from a common pump cylinder in which thevseveral quantities of liquid subjected to delivery pressure during different delivery periods, which quantities will for convenience hereinafter be referred to as columns of liquid or liquid columns, are subjected to the influence of compensating factors to insure delivery of liquid to the several points of consumption in quantities which have definitely predetermined relationship, i More particularly, the invention aims at the provision of improved struck:i5 ture whereby pumps of the character under con- Fig. 1 is a section through a pump embodying the invention, the upper portion of the figure being taken on line l--l of Fig. 4, and the figure further showing one of the pump outlets connected to a` fuel injector of an engine; 55 Fig. 2 is another section of the upper part of (Cl. 12S-139) the pump shown in Fig. 1 taken on the line- 2-2 of Fig. 4;

Fig. 3 is a section of a part of the pump shown in Fig. 1 taken on the line 3-3 of Fig. 4;

Fig. 4 is a top plan view of the pump shown '5 in Fig. 1;

Fig. 5 is a developed view of part of the cylinder and plunger structure of Figs. 1 to 3;

Figs. 6 and '7 are diagrams illustrative of certain characteristics of pump operation; '19

Fig. 8 is a fragmentary section showing a variation of part of the pump structure shown in Figs. l and 2; l

Fig. `9 is a fragmentary section showing still another variation of the same portion of the 15 pump structure; and y Figs. 10 and 11 are more or less diagrammatic top plan views showing different applications, embodying the invention, of pumps to internal coml bustion engines.

Referring now more particularly to Figs. 1 to 5, the pump 'illustrated comprises a casing consisting of a main casing part I0 and a head part I2.

A pump cylinder or barrel I4 is fixed ink a recess is in the head part lz by means ef e threaded. 25 nipple I8 and the cylinder has reciprocably and rturnably mounted in the bore thereof the pump plunger 20, at the inner end of which is located the pump chamber 22 to which liquid is admittedl 4through the suction line 24 and spring loaded 3 suction valve 26.

In the lower portion of the casing part l0 a cam shaft 28 is mounted in suitable bearings 30. Shaft 28 carries cam 32 which is in vcontact with roller 34 in the lower part of tappet 36slidably 35 mounted in a suitable bore in Ithe casing part. The upper portion of the tappeti is formed with a. cylindrical recess having a circular wall 38. The lower end of the plunger 20 is enlarged to form a foot 20a resting in the bottom of the recess 40 and held in position by a spring retaining Washer between which and the pump barrel there is compressed the pump spring 42 which acts to cause the tappet and plunger to follow the reciprocating path of travel determined by the profile of cam 32.

Thehead part of the pump casing is provided with four delivery passages 44, 46, 4B, and 50 (see Figs. 1 and 2) which communicate respectively '50 with the pump outlets 52, 54, 56, and, in Teach case by way of a spring loaded pumpdelivery valve. Each of the delivery valves is of like construction and all have been designated by refer-- ence character 60.

The pump barrel It is provided with a series of delivery ports di, d2, d3, and d4 which form respectively the inlets for the delivery passages 44-50 and which are placed in communication with the portions of the respective delivery passages located in the head of the pump casing by means of channels constituting in effect extensions of the delivery passage portions in the head and designated respectively as 66a, 66a, d8a, and 50a.

For convenience the pump outlets are uniformly distributed around the pump, as shown in Fig. 4, and for clarity of illustration the delivery ports and portions of the delivery passages adjacent thereto have been shown distributed around the circumference of the pump barrel with uniform angular displacement of between ports, in order to' bring the ports into the planes of Figs. 1 and 2. For reasons which will hereinafter be more fully explained, the location of the ports yperipherally of thecyllnder bore may be somewhat different in practice.

I'he pump cylinder is further provided with a vertically aligned row of outlet or relief ports r1, rz, r3, and r4 communicating through suitable transverse bores in the barrel with a common overow chamber 62 formed between the upper portion of the cylinder barrel and the wall of the recess I6 in the head I2. 'I'he overow recess |6 is in communication with a suitable overow outlet 64.

Relief ports n n are located at the same height in the pump barrel as delivery ports Z1-d4, respectively, and further are located in an axial plane different from the axial plane of any of the delivery ports.

The pump plunger is provided intermediate its ends With\a circumferentially extending recess 66 which is in communication with the pump chamber by way of passage 66a in the plunger.

One portion of the recess 66, extending circumferentially of the plunger a suiiicient distance to be in line with each of the overow ports in the pump cylinder, which for convenience will be referred to as cylinder overiiow ports, provides a plunger delivery port 68, various sections of which appear in Figs. 1 and 2. As will beobserved from Fig. 3, an island-like projection 10, the outer surface of which is in contact with the cylinder bore, extends from the recess 66 to provide two axially spaced plunger overflow ports. 12 vand 14. The projection 'l0 provides an -inclined control edge 10a for part load control of the quantities of liquid delivered by the pump, diiferent portions of this inclined edge registering with the line of ove'ow ports,

indifferent positions of rotation of the plunger.

To effect the rotational adjustment of the plunger, a sector 'I6 is mounted for! turning movement in the casing around the upper portion of thev tappet 36. Sector 16 has external teeth 18 meshing with the teeth of a rack 80 slidably mounted in the pump casing and adapted to be actuated from any desired source ofcontrol (not shown). The inner face of `sector 16 is provided with a vertical slot 82 which receives the outer end of a` pin 84 passing through an arcuate slot 86 in the wall of the tap-` pet and the inner end of whichv is xed in the foot 28a of the plunger. The tappet is further provided with a vertical slot 88 in which slides the inner end of alocating pin 90 xed in the pump casing to prevent turning movement i the tappet. It will be evident from Fig. 1 that movement of the rack 88 along an axis normal to the plane of the paper will result, in turning movement of the plunger.

Referring now more particularly to Fig. 5, in which the cylinder and plunger construction, inclusive of ports, is illustrated in developed form, the cylinder relief ports r1r4, are shown in their in-line position as in Fig. 3, but the cylin- .der delivery ports di, da, da, and di are shown peripherally displaced from the positions which have been illustrated for the sake of clarity in Figs. 1 and 2; As diagrammatically shown in Figs. 1 and 2, 90 is the maximum angular displacement between delivery ports and in order to provide sumcienit circumferential displace,- ment between cylinder delivery ports to permit the control projection 10 on the plunger to operate properly in diierent positions of rotation of the plunger, one or more of the delivery ports are in pradtice advantageously displaced circumferentially from the positions shown in Figs. l and 2 to provide a greater peripheral distance between the line of overow ports and the nearest delivery port. Conveniently, the delivery ports are arranged. peripherally as indicated in Fig. 5, with ports d1 and dz in one axial plane to one side of the relief ports and ports d3 and d4 in another axial plane to another side of these ports. The delivery ports whenso displaced are connected respectively to the uniformly distributed delivery passages in the head by any suitable arrangement and location of the passages in the pump barrel, as will readily be understood by the reader. The operation of the above described pump is as follows, sumed that the plunger is in the full load position shown in Fig. 5 and ascending on its delivery stroke with the pump chamber filled with liquid from a preceding suction stroke. As will be apparent from Figs. 1, 3, and 5, the plunger, in the position shown in these ilgures,zhas moved to a position in which the plunger delivery port 68 and the cylinder delivery port di are in registry and in which the plunger overow port 'l2 y has just passed out of registry with the cylinder overilow port ri. In this position commencement of delivery through port d1 is just occurring and will continue until the plunger overow port 'Il comes into communication with the cylinder overflow port n to terminate the period of delivery through port di. By the time this occurs, plunger overiiow port 'l2 is in communication with the cylinder overow port 12 to permit continued movement of the plunger in the direction of its delivery stroke and port 68 has come into communication with delivery port d2. As soon as the plunger overiiow port 12 passes cylinder overflow port r2, a second delivery period will commence, which eil'ects delivery through Dort dz. 'I'his second delivery period continues until plunger overflow port 14 comes into communication with cylinder overow port r2. 'This cycle of events is repeated respectively with reference to ports da and ra andwith respect to ports d4 and r4 as the plunger continues to move on its delivery stroke, thus providing a alternating with a Referring now more particularly to Fig. 6, the

ordinates of the diagram shown in this figure represent the quantity (Q) of liquid delivered during a delivery or injection period and the absissa represent rotation of the pump cam shaft (R) in degrees. If the several outlets of the pump are assumed to' be connected to different injectors, one of which is indicated at 18 in Fig. 1 and which is shown as provided with a spring loaded delivery valve 60a, and if the speed of rotationof the cam shaft is constant, the quantities of fuel forced from any one nozare equal to each other and are proportional to the pressure (P) ln the fuel delivery passages and lines. Under this assumed condition the ordinates of the diagram 'indicate pressure as well as quantity. Theoretically, the pressure in the4 pump chamber and in the delivery line during a delivery period can rise along the line A-B, the delivery valve 60a (Fig. 1) then opening to effect delivery along the line B-C through the nozzle of the injector. At point C the pump is unloaded. In actual practice, however, injection does not take place in the above outlined theoretical mannen The speed of the pump cam shaft is dependent upon the speed of the 40 engine and the speed of the plunger is dependent during the delivery period on the cam shaft speed. In the following analysis it has been assumed, for the sake of simplicity, that during a delivery period there is no change of speed so 45 that the delivery stroke for each delivery period is carried out at approximately constant speed corresponding to the prevailing speed of rotation of the pump cam shaft. The form of the curve representing fuel delivery depends in part 50 on the degree of compressibility of the injected fuel. From examination of injection occurring through an injection nozzle, the quantity Q) of fuel injected, as a function of the pressure drop, is determined by the following equation= where a indicates the injection nozzle outflow coeilicient;

F the cross-section of the nozzle orifice or sum of the cross sections of all nozzle orifices;

g acceleration due to gravity;

p the pressure drop across the nozzle orifice, that is the injection pressure minus the cylinder pressure; and

ry the specific gravity of the fuel.

The following relationship exists between the pressure rise in the fuel column ahead of the pump plunger, and the time:

where A denotes the cross-section of the pump 75 plunger;

of fuel from the injection nozzle.

zle per unit of time, (for example, per second) B the volume of fuel supported by the pump plunger at the beginning of a delivery period;

l0 .I C Mw/2a y v is the speed of the pump plunger; and a the compressibility of the fuel.

Differential Equation (2) shows that after commencement lof the application of pressure by the pump plunger, there occurs a volumetric alteration in the column of fuel subjected 'to pressure by the pump plunger, which column includes the liquid under pressure in the pump and in the delivery line leading to the injector. This alteration in volume is partly due to compression of the liquid and partly due to the passage n The course of the variation in pressure is thus dependent on the volume of the fuel column and on the quantity of fuel injected, the latter being proportional to the square root of the pressure.

VUnder no circumstances, therefore, does the pressure rise perpendicularly in correspondence with the line A-B. but rises gradually, for example in accordance with curves such as those shown at a, b, and c on the diagram. Curve a represents the character ofpressure rise. occurring in pumps having smaller volume than that of pumps in which the pressure rise is in accordance with curve c. Such being the case it is evident that curve b represents the character At the point C a pump overflow or relief port is opened to unload the pump and terminate the delivery period. Until the delivery valve 60a closes, fuel ows through the pump overflow passage of the pump. Theoretically, the pressure should fall along the line C-D of Fig. 6 but in practice there is a considerable lag or retardation of the pressure drop. In practice the pressure drop on release follows a curve such as indicated by C-E on the diagram. When the delivery valve 60a is closed, the portion of the fuel column between said valve and the nozzle orifice or orifices expands through the latter into the combustion chamber of the engine. The delivery valve may in known mannerbe disposed in the body of the injector as herein illustrated only a slight distance ahead of the nozzle. Only inthe case 4of fuel injection devices without delivery valves, that is, if the structure were as indicated in Fig. 1 butgyhdut a delivery vaive,

. does the pressure dro' substantially in accordv ance with the theoreti al line C-D.

The compressibility of the fuel affects the eiliciency of the pump. 'I'he volumetric efficiency of the pump is determined by the ratio of the areas ACEzABCD. For `this reason pumps having delivery valves therefore have a higher volumetric efiiciency than pumps without delivery valves.

Diierences in the volumes of liquid may also occur, inter alia, for reasons of pump design. Thus, multi-cylinder pumps always show small deviations in the volumetric capacities of the different fuel chambers and passages. The diagram of Fig. 7 illustrates the different volumetric eiliciencies V and V1 of two cylinders of a multicylinder fuel pump at different pump speeds N. This fact is one of very great practical importance, particularly when thepump is applied to a an internal combustion engine of the injection type, since if the different cylinders of the same engine have injected thereinto different amounts of fuel. the desired steady and even running of the engine, with equal power output from each of the cylinders at any given load, will be materially and adversely aiected.

In the case of a pump in which a series of delivery periods are eiected from a single cylinder during the course of one delivery stroke of the plunger, it is evident that the fuel column in the pump chamber becomes progressively smaller for each such delivery period. Consequently, if the desired equality of delivery during the several delivery periods is to be obtained, equalization must be provided in order that the plunger may have approximately the same volume of fuel in front of it during each delivery period.

In accordance with the present invention this may be provided for in different ways, some of which will now be described by way of example.

Referring now to Figs. l and 2, it Will be observedthat the delivery passage lll through which liquid is delivered during the rst delivery period when the volume of liquid in chamber 22 is the greatest, discharges into a relatively very small chamber ahead of the appropriate delivery valve 60. Delivery passage 46 through which the next delivery period is effected, at a time when the volume of liquid in the pump chamber is less than when delivery is effected through passage 44, discharges to a chamber 82 the capacity of which is larger than that of chamber 8D and which is likewise situated ahead of the appropriate delivery valve. In similar manner passages 48 and 50 (Fig. 2), through which delivery is effected in sequence during periods in which the volume of liquid in the pump chamber is in each case smaller th-an during the preceding delivery period, discharge respectively to chambers Bt and 86, chamber 8d being of larger capacity than chamber 82 and chamber 86 being of larger capacity than chamber 84. These chambers may, for convenience, be designated as compensating or equalizing chambers. In the construction ilflustrated in Figs. 1 and 2, the equalizing cham- /bers are conveniently formed, as shown, by drilling to different predetermined distances, the bottom portion of the recesses in the head of the pump which receive the diiferent delivery valve assemblies.

Another -arrangement for providing equalizing chambers of dilerent capacity is illustrated in Fig. 8 in which each delivery passage, passage 50 being shown by way -of example in the gure,is intersected by a bore 88 closed by a threaded plug 90 which may be adjusted to secure the desired capacity of the compensating chamber 86a formed at the inner end of the bore The position ofv plug 90 is advantageously fixed by a lock nut 92` and the exposed end of the plug protected by a suitable cover or cap 94.

4In Fig. 9 another arrangement is illustrated in which the compensating chamber 86h is formed between. the bottom of the delivery valve assembly and the bottom of the recess which receives it by means of a spacing ring 96 th-e Width of which will evidently determine the volume of the compensating chamber. It will be readily appreciated that the desired compensating chambers of different volume may readily'be `obtained with this arrangement by utilizing spacing rings of different width located at the bottoms of cavities of like form in the pump-A head.

To la certain extent, volumetric equalization of the fuel columns to different injectors may be enected by providing fuel lines leading from the pump unit to the several injectors, which lines are of unequal volumetric capacity. Such unequal volumetric capacity may be eiected by provision of lines of unequal length and equal internal diameter or by utilizing lines having different internal diameters, or both.

As illustrated in Fig. 10, the delivery lines 98a, 98h, 98e, and 98d are of equal diameter and unequal length, the arrangement being such that the shortest line 98a is attached to pump outlet 52 through which delivery is eiected when the pumpA chamber has maximum volume, the remaining lines of progressively increasing length being connected to the pump outlets in the order of progressively decreasing pump chamber volume. The cylinders to which these lines are connected are indicated in Fig. 10 as the cylinders of a four cylinder engine with a conventional 1 2-4-3 firing order.

In Fig. 11 another arrangement is illustrated in which lines Illa, |002), |000, and l00d of different size ar-e connected to the pump outlets in a relation such that the volumes of the respective lines are progressively greater for delivery periods during which the pump chamber volumes are progressively smaller. The engine shown in Fig. l1, like that shown in Fig. 10, is one having the conventional 1-2-4-3 ring order.

From the foregoing description it will be apparent that the principles of the invention may be embodied in various different structural forms and the invention is accordingly to be understood as embracing all forms of construction falling within the scope of the appended claims when they are construed as broadly as is consistent with the state of the prior art.

What is claimed is:

1. A plunger pump including a pump cylinder having a series of delivery outlets and separate conduits for conducting liquid under pressure from the pump chamber through different outlets to diierent places of consumption during different delivery periods, diierent ones of said conduits having diierent volumetric capacities for the liquid under pressure therein during the respective delivery periods, and the volumetric capacity of a conduit through which liquid is delivered later in the delivery stroke of the plunger being greater than the volumetric capacity of a conduit to which liquid is delivered earlier in the delivery stroke of the plunger.

2. A plunger pump including a cylinder, a plurality of pump outlets and separate conduits placing different outlets in communication with the pump chamber at different times during the delivery stroke ofthe plunger, said conduits having different volumetric capacities and the relation to each other of the capacities of the different conduits being the inverse of the relation of the volumetric capacity of the pump chamber at the different times when delivery iseiected through different conduits.

3. A plunger pump including a cylinder, a plurality of delivery passages, diierent passages being in communication with the pump chamber at diierent times during the delivery stroke of the plunger, and at least certain of said passages having an equalizing chamber associated therewith for establishing liquid columns of substantially equal volume subjected to delivery pressure when the diierent passages are in communication with the pump chamber.

4. A plunger pump Aincluding a cylinder, 'a plurality of delivery passages, different passages being in communication with the pump chamber at different times du'ring the delivery stroke of the plunger, at least certainof said passages having an equalizing chamber associated therewith, and means adjustable to Vary the volumetric capacities of said equalizing chambers.

5. A plunger pump including a cylinder, a plurality of delivery passages, dierent passages being in communication with the pump chamber at diierent times during the delivery stroke of the plunger, at least certain of said passages having an equalizing chamber associated therewith, said equalizing chambers being formed between diierent pump parts removably secured together and spacing elements between said parts for determining thevolumes of the diierent chambers formed between them.

6. A plunger pump including a cylinder, a plurality of pump outlets, a plurality of delivery passages, dierent passages serving to separately connect the pump chamber to diierent outlets in different positions of the plunger on its delivery stroke, a pump delivery valve for each passage, and at least certain of said passages having an equalizing chamber associated therewith between the pump cylinder and the associated delivery valve, different chambers having different volumes to compensate for the dierent volumes of the pump chamber at the different times in the delivery stroke of the plunger when the different passages are brought into communication with the pump chamber.

7. In a fuel injection system for internal combustion engines, the combination with a fuel pump of the plunger type and a plurality of fuel injectors for supplying fuel at diierent times to diierent engine cylinders, of a plurality of fuel delivery lines separately connecting different pump outlets to different injectors, said delivery lines having different volumetric capacities proportioned relative to each other and to the internal volumetric capacity of the pump at different delivery periods to compensate for different pump chamber volumes during different delivery periods.

8. In a fuel injection system for internal combustion engines, the combination with a plunger pump including a pump cylinder and a plurality of pump outlets, different outlets communicating with the pump cylinder at different times during the delivery stroke of the plunger, and a plurality of fuel injectors each provided with a delivery valve determining the fuel pressure required to initiate injection, of a plurality of fuel lines each connecting a different pump outlet with a different injector, the value of the volumetric capacity of each of said fuel lines being such that when added to the volumetric capacity of the delivery passage in the pump with which it communicates and the volume of the pump chamber when communication between it and the pump chamber is established, the volume of the liquid column subjected to delivery pressure is substantially equal to the volume of the equivalent liquid column subjected to delivery pressure for delivery through any other of said lines.

9. A plunger pump for supplying liquid under pressure from a common pump chamber to different places of consumption at diierent times during the discharge stroke of the pump plunger through separate delivery lines, and compensating means associated with the pump for compensating for the dierence between the volumes in said pump chamber at the commencement of each of the diierent delivery periods to establish substantially equal volumetric relation between the quantities of liquid subjected to de livery pressure at the commencement of each delivery period. t 4

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